In the LTE system, the system information can be classified into main system information (MIB) and general system information (SI). Wherein, the MIB is transmitted on the broadcast channel with a fixed transmission period of 40 ms, i.e., the first transmission of the MIB in a period happens always when SFN (System Frame Number) MOD 4=0 (i.e., SFN %4=0). The SI is transmitted on the downlink shared channel, wherein system information 1 (SI-1) is transmitted with a fixed transmission period of 80 ms, i.e., the first transmission of the SI-1 in a period happens always when SFN MOD 8=0. The scheduling information of the other SIs is included in the SI-1, comprising parameters such as scheduling period and transmission window. A terminal can deduce the time or time range of the transmission of the SI from such scheduling information. The transmission of the system information employs a dedicated Hybrid Automatic Repeat Request (HARQ for short), and employs a dedicated Radio Network Temporary Identifier (RNTI for short) on the Dedicated Physical Control Channel (DPCCH for short) to distinguish it from other downlink signaling or data.
In view of a terminal, the receiving process of the system information is as follows: after the process of cell searching, the terminal first receives an MIB, receives the content of the SI-1 according to the scheduling features of the SI-1, deduces the scheduling rule of the other SIs from the SI-1, and then performs the receiving in a specified time. When receiving the SI, the terminal obtains the description information, such as frequency resource and Modulation and Coding Scheme (MCS for short), of the wireless resource carrying the SI from the DPCCH corresponding to the SI, i.e., the resource scheduling of the SI is dynamic.
Related system parameters are often incorporated into one System Information Block (SIB for short), for example, the parameters related to the cell reselection will be organized in the same SIB, and one or more SIBs can be included in one SI. Obviously, the scheduling periods of these SIBs are the same, but the SIBs with the same scheduling period are not always contained in one SI, i.e., it is allowed that different SIs have the same scheduling period, for instance, the SIs of neighboring cells, wherein the neighboring cells can be classified into in-frequency neighboring cells, inter-frequency neighboring cells, GSM/EDGE Radio Access Network (GERAN) neighboring cells, UMTS Terrestrial Radio Access Network (UTRAN) neighboring cells, and Code Division Multiple Access (CDMA) 2000 neighboring cells, etc.
In order to improve the coverage range of the system information, the MIB and the SI will be both retransmitted in one scheduling period. For example, the MIB will be retransmitted for 4 times in the period of 40 ms. In general, the SI can be retransmitted in two manners, i.e., continuous retransmission manner and discrete retransmission manner. The continuous retransmission manner means that the retransmission of the SI is completed in one relatively short time window, and the terminal shall continuously receive the retransmitted content in this time window. The discrete retransmission manner means that there is a certain time interval between the retransmitted content, and the terminal does not need to continuously receive between two retransmissions. The greatest benefit of the discrete retransmission lies in that the receiving time diversity for the terminal is increased.
The network constantly retransmits the MIBs and the SIs according to the scheduling rule, but it is not necessary for a certain terminal to always receive all the MIBs and the SIs, because the system information is periodically broadcasted content, and after a terminal has read out valid system information, the terminal can choose to skip the received SIs, unless the content of the system information has been changed or the terminal can not determine whether the valid system information has been stored. Another reason is that different terminals have different terminal capabilities. For some terminals, for example, for the terminals not supporting the CDMA2000, the SIs of a neighboring cell in the CDMA2000 are invalid to them, thus the terminals also can choose not to read out the SIs containing the CDMA2000 all the time. However, the premise for such kind of a terminal behavior is that the terminals should clearly know the starting time and the ending time of the transmission of a certain SI.
However, sometimes a terminal can not determine the starting time and the ending time of the transmission of an SI merely according to the scheduling period of the SI, because the scheduling periods of the SIs often have a relationship that one is simply a multiple times of another, and even some SIs have the same scheduling period. For instance, SI-1 has a scheduling period of 80 ms, SI-2 has a scheduling period of 160 ms, SI-3 and SI-4 have a scheduling period of 320 ms, then SI-1, SI-2, SI-3 and SI-4 will appear simultaneously at the radio frame with SFN MOD 8=0, such as SFN=320. It should be noted that SI-3 and SI-4 are always scheduled in an overlap way, and in this case the terminal can not determine the starting time and the ending time for SI-3 and SI-4, thus the terminal can not selectively receive the system information with accuracy.
During the current process of the transmission of the system information, it is not allowed to have an overlap phenomenon of the retransmission between the SI-1 and other system information. Since the scheduling period of the SI-1 is fixed, i.e., 80 ms, the space left for other SIs will be very small if the SI-1 needs to be retransmitted for many times in the period. For instance, if the SI-1 needs to be retransmitted for 4 times, the SI-1 will occupy 4 radio frames because in each radio frame SI-1 can only be transmitted once, thus there are only 4 radio frames left for other system information, i.e., 40 ms. Obviously, the retransmission of the SI-1 will affect the scheduling for other system information, therefore a technology for solving this problem is desired.